Federal prosecutors in New York are preparing to file criminal charges as early as this week against two Bureau of Prisons workers who were supposed to check regularly on millionaire sex offender Jeffrey Epstein the night he hanged himself in his cell, according to people familiar with the matter.

The two corrections workers, whose names have not been released, fell under suspicion immediately after Epstein was found early on the morning of Aug. 10 in his cell at the Metropolitan Correctional Center, a federal jail used primarily for people awaiting trial.

The New York City medical examiner ruled his death a suicide by hanging, although lawyers for the disgraced financier have questioned that conclusion.

At the time of his death, the 66-year-old Epstein had been at the facility in Lower Manhattan for more than a month on sex trafficking charges that could have led to a prison sentence of as much as 45 years. He had pleaded not guilty, and the case was due to go to trial next year.

The death of the most high-profile defendant in the federal prison system led to a major shake-up at the Bureau of Prisons. Attorney General William P. Barr brought in a former director of the agency to run it again, and replaced the top official at the MCC, saying the preliminary investigation had found “serious irregularities at the center.”

Those irregularities include logs indicating that Epstein was checked on regularly, in accordance with MCC procedures. Investigators don’t believe those checks happened, according to the people familiar with the matter, who spoke on the condition of anonymity to discuss an ongoing investigation. The two staffers were placed on leave shortly after Epstein’s death.

Prosecutors have been focused on charges against the officers of falsifying federal records, people familiar with the matter said. In recent weeks, they sought to have the officers plead guilty, though they refused, the people said.

A spokesman for the U.S. attorney in Manhattan declined to comment.

The corrections officers union has said the MCC has been notoriously understaffed and its officers overworked, including the two on duty that night.

The investigations already have found a troubling lack of follow-through by Bureau of Prisons personnel after a July 23 incident in which Epstein may have tried to kill himself, according to people familiar with them.

In that incident, guards rushed to Epstein’s cell when his cellmate at the time, Nicholas Tartaglione, began yelling, according to these people. Tartaglione told officers he had noticed that Epstein had a bedsheet around his neck and appeared to be trying to kill himself, the people said.

Epstein denied that, they said, and told prison staff that he had been attacked — something Tar­taglione denied.

Some MCC staff doubted Epstein’s claim, suspecting instead that he either faked a suicide attempt or intended to take his own life, the people said.

Epstein was placed on suicide watch, but officials lifted those measures six days later, on July 29. On that day, MCC officials returned Epstein to a special housing unit known as Nine South — where officers were directed to check on him in his cell every 30 minutes. The other explicit condition of his removal from suicide watch was that Epstein would not be left alone in a cell — although he was, these people said.

In 2008, Epstein pleaded guilty in Florida to state charges based on allegations that he paid underage girls for sex acts. That plea deal was part of an agreement with federal prosecutors that has been criticized as too lenient.